The present invention relates generally to lighting fixtures, as in particular to a track mounted lighting fixture for a sealed beam lamp.
Track mounted lighting fixtures for sealed beam lamps are known, such as disclosed in U.S. Pat. No. 4,727,460 in which the fixture includes a pair of U-shaped members having a space for receiving the rim of a sealed beam lamp therebetweeen in the bight region of the two U-shaped members. A pair of springs urge the lamp into the bight of the U-shaped members.The U-shaped members are firmly connected to a bridging member which is pivotally and slidably secured to a support arm by means of a threaded knob. The support arm is connected to a track adaptor. The bridging member has a flat surface at one end and the knob also has a flat surface. The flat surfaces engage either side of the support arm either directly or through the intermediary of a washer to provide a bearing surface for rotation of the bridging member. The manually operable knob is provided to tighten or loosen the clamping arrangement between the bridging member, support arm and knob to prevent or permit rotation and vertical sliding of the bridging member relative to the support arm.
Difficulties can arise in assuring proper positioning of the sealed beam lamp in that such lamps are made by third party sources and variances in the thickness of the rim of the lamp is beyond the control of the fixture manufacture. Thus, if an overly thick rim is encountered, there may be difficulty in having the rim fit in the space between the two U-shaped portions.
Further, actuation of the knob to achieve a repositioning of the angle of the lamp is oftentimes inconvenient because of the mounted position of the fixture on a back lighting system.